Biological Effects of Radiation Part Two

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Effects from Non-Acute Radiation Doses

Biological effects from non-acute radiation exposures are dependent on damage to specific targets in the cells, such as DNA. These type of effects, such as cancer, occur probabilistically. The lower the level of radiation dose, the lower the probability of damage being done to a sensitive target in the cell. Although the odds of damaging a sensitive target may be small, it is prudent to make efforts to reduce radiation exposures whenever possible. This is why the University of Washington has an ALARA program, which promotes workers to maintain the lowest reasonable radiation dose level for the type of work that is performed.

Instances of radiation induced cancer are extremely rare when compared with the prevalence of naturally occurring cancers. In 1997 the National Cancer Society reported that the risk of dying from cancer is 25%. For comparison, the National Committee on Radiation Protection reported (NCRP Report No. 116) that if a person received 1000 mrem, they would increase their risk of fatal cancer by 0.04% in other words in a population of 10,000 people, 2500 will have some form of cancer and if all these people received 1000 mrem there would be an additional 4 cancers. Since dental x-ray workers only receive a small fraction of this dose each year, it is evident that the risk of radiation-induced cancers for dental workers is extremely small.

Radiation does not cause any new or unique type of disease or malformation. All biological effects from non-acute radiation exposures also occur in the general population from natural causes.

Other non-acute effects include damage to genetic material in the reproductive cells, which could cause cancer or malformations in the offspring of the exposed person. Current data indicate that the risks of these types of effects are much lower than the corresponding risks of cancer induction discussed above. Genetic effects in offspring have not been seen in human populations.

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